Fluorescent lamp mount



Feb 9, 1965 H. R. KESTNER ETAL 3,169,205

FLuoREscENT LAMP MOUNT Filed April 5, 1961 '2,9 IDVGDTOVS:

Robecl: A. Huvebbe Theny AelfiOT-heg Havo Ld 1Q. Hescime United StatesPatent O Hamid R.. Kastner, Maycid Heights, and Robert A. Kuehler,Cieveiand Heights, Ghia, assignors to Generali iiieetric Company, acorporation of New York Fitted Apr. S, 1196i, Ser. No. 1%,892 il@lairns. (Qi. 3h30-iti?) This invention relates to the manufacture offluorescent lamps and in particular to the structure and manufacture ofthe mounts through Whichfvare sealed the lead-in wires Y applyingY thecoating.

The object of the invention is to provide a solution to the clear spotproblem as stated above.

investigation of this problem has traced it to the gas filling of thelamp on the exhaust machine. In the processing of fluorescent lamps, theelongated tubes which form the envelopes of the lamps are first coatedinternally with a phosphor by causing the phosphor suspension to flowtherethrough yand afterwards drying it. yThe next step involves thesealing machine on which the lamp mounts through which extend thelead-in wires that support the electrodes, are sealed into the ends ofthe envelope. Following sealing, the lanp is processed on the exhaustrnachine where the electrodes are activated by passing cur- :rentthrough the filaments in order to heat and decompose the alkaline earthcarbonate coating thereon to alkaline earth oxide. At the same time thelamp is evacuated to remove the air and any gases and vapors includingcarbon dioxide resulting from the decomposition of the alkaline earthcarbonatos. The exhaust of the lamp is performed through the exhausttube of one of the mounts which was previously blown open at the pressfor this purpose. Finally, at one of the last positions on the exhaustinfachine, an inert filling gas is added and a small measured quantityor dose of mercury -is released into the lampy sure of a few millimetersof mercury, for instance at 2 to 3 millimeters.

Surprisingly enough, considering the low filling pressure and therelatively srn-all mas-s ofgas involved, we have determined that it isthe addition of the ll gas which causes the clear spot in the phosphorcoating next to the mount. The gas lilling system ycommonly used isessentially a constant mass-flow typewith a restrictiony controlling therate of flow from a pressurized source such as a high pressure cylinder.The blow-out of the conventional mountdesign which `has been commonlyused in iiuorescent ylamp manufacture directs the gas jet at an `angleof about 30 relative yto the tube wall. The angle of the blow-out,together with the fact that there maybe some slight constriction `at theexit, results in a gas jet of suihcient force to blow the phosphorcoating off the Wall.

We have considered and discardedvarious possible solutions to thisproblem. For instance the use of a truly axial mount with a blow-out atthe tip of the press along the axis of the exhaust tubeis noty desirablebecause it presents majorrnanufacturing diiiiculties. The mercury doseis formed in accordance with the invention.

3,169,205 Patented Feb. 9, 1965 ice released into the lamp lthrough theexhaust tube and the cathode filament coated with emission mix extendsacross the axis of the mount. Since the lamp is vertically supported atthis time, the mercury charge would strike the filament with thepossibility of dislodging rthe emission mix coating. offsetting thecathode to one side of the axis is not a satisfactory solution becauseit introduces further complications in mount manufacture, and moreoverlamp appeanance is adversely affected.

` In accordance with the invention, we have satisfactorily resolved4 theproblem by modifying the shape of the blow-out aperture at the press ofthe exhaust tube. We have flared the exit aperture and increased itswidth in a direction perpendicular to the axis of the exhaust tube, andwe have changed the direction of the blow-out aperture by continuing itinto a grooved channel formed in the side of the press and extendingtowards its end. Preferably the grooved channel makes but a shallowangle relative to the exhaust tube or lamp axis. These modificationshave substantially eliminated clear or thin spot formation in thephosphor coating at gas ill.L

For further objects and advantages and for a detaile explanation `of theinvention, attention is now directed to the following description of apreferred embodiment taken in conjunction with the accompanying drawing.The features of the invention believed to be novel will be moreparticularly pointed out in the appended claims` In the drawing: v r

FiG. 1 is a side View, foreshortened and partly sectioned, of afluorescent lamp embodying the invention.

FIGQZ is a side view of a convention-al mount operatively positionedrelative to la mechanism forreforming the blow-out aperture.

FIG. 3 shows the same mount as in FIG. Zwith the reforming jaws actuatedup into engagement with the mount press.

FIG. 4 is a side cross-sectional view of the mount re- FIG. 5 is a sideview of the reformed mount rotated on its axis 90 relative to FIG. 4 soas to place the wide curved surface of the blow-out aperture in theplane of the drawing.

The typical lamp illustrated inthe drawing comprises a vitreous envelopei which iscoated internally with a phosphor indicated by the .dottedline .at 2.V `To each end of the lamp a mount is sealed such asindicated at 3 in FIG. 2 for the case of the conventional mountheretofore used, yand at 3a in FIGS. 4 and 5 for the improved quasiaxialblow-out mount kin accordance with the invention.

Referring to FiG. 2, the -conventional mount y3' cornprises a stern tubewhich is formed into aflare i into about the ends of the filament 9which is Vcoated with alkaline earth carbonate emission mix asindicatedat yit) in FIG. 5.v in FIG. 2, the mount 3 has a blow-out aperture illwith an exit surface` i2 at a stecpanglerelative to the axis oftheexhaust tube. This causes the gas jet which forms during the inert gaslling operation-to strike with considerable force the envelope Wallandto blow off the phosphor coating leaving a spot in the regionindicated at i3 in FIG. l whichis either clear or only verythinlyicoated with phosphor.y

In accordance with the illustrated embodiment of the invention, theblow-out aperture ofthe mountis reformed Vto provide a flaring exitaperture 14 and a relatively wide grooved channel l5 in the side of thepress and extending towards the end, as indicated in FIGS. 4 and 5. Thereforming of the blow-out aperture may be doneon a mount or stem machinewherein the mount is supported inverted position by means of jaws luwhich grip the exhaust tube, as conventionally indicated in FEGS. 2 and3. The blow-out aperture fill shown in FiG. 2 was ormed in conventionalfashion at an earlier station on the stem machine by blowing a puit ofair through the exhaust tube while lires are played on the sides of thepress to maintain the glass in a viscous state. The reforming of thepress to give the desired blow-out contour is done by means of matrixjaws i7, i8, shown in FlGS. 2 and 3. l aw i7 is provided with a roundedinclined ridge i@ while jaw 18 is provided with a relief V 2u. rfhematrix jaws are mounted on pivoting levers 2l, ZZ which are actuated bymeans of links 23, 24 from a vertically reciprocating crosshead 25. InFIG. 2, the jaws and levers are shown in their outswung retractedposition whereas in FlG. 3 2they are shown in their upswung positionengaging the press of the mount. The glass engaging surfaces of thematrix jaws diverge slightly in the direction ot the filament so thatexcess glass not displaced laterally is forced down in the direction ofthe iilament and may lengths the press slightly.

In conventional mount making, the blow-out aperturev may occurhaphazardly on either side of the press, that is to the right as shownin FlG. 2, or to the left. For the present purpose, it is necessary thatthe blow-out always occur on the same side. This is achieved byoffsetting the press-forming jaws to one side of the axis of the exhaustand stem tubes at the first pressing. This results in a press o asillustrated in FiG. 2 wi `h slightly less glass on one (right as seen inthe drawing) side ot the axis than on the other. Then when the blow-outis formed, it forms preferentially on the side having the less glass.This preferential forming may be further assisted by making the tiresslightly hotter on the side of the mount where the low-out is desired toform.

The contour of the improved mount in accordance with the invention isshown in FGS. 4 and 5. The exit aperture i4 iiares outwardly and iscontinued into a grooved channel iS'extending between the lead-in wirestowards the end of the press. The central portion of the wall oi channel15, which may be referred to as the exit surface, makes a shallow anglebetween 5 and 15, preferably about 9, to the axis of the exhaust tubewhich is also the longitudinal axis of the lamp envelope. Furthermore,as best seen in FG. 5, the exit aperture ld and the grooved channel 1Sare widened transversely to the axis of the exhaust tube substantiallyin excess of the internal diameter of the passage through the exhausttube. This combination of features insures that the filling gas jetemerges at a relatively shallow angle with respect to the envelope walland with a lessened velocity. in other words, the gas jet is almostparallel to the lamp axis and has less force with the result that thephosphor is not blown off. At the same time, the shallow angle of theexit surface insures that when the mercury dose (shown as a drop 26 inFIG. l) is released into the lamp through the exhaust tube, it isdeiiected olf axis and does not strike the :filament 9. Thusthepossibility of dislodging emission coating from the filament is avoided.

The more common manufacturing procedure is to exhaust and gas till thelamp from one end only, that is from the top end which would have mount3a. ln such case a so-called dummy mount 3b is used at the other end.The dummy mount may be similar to the conventional mount 3 shown in FIG.2 except that the exhaust tube is not blown out at the press. An exhausttube may nevertheless be provided to facilitate locating the end of thelamp in the clamp or holder therefor on the exhaust machine. However, ifin order to further increase the machine speed it is desired to exhaustand gas iill from both ends of the lamp, then in such case both ends ofthe lamps would be provided with the improved mount 3a according to theinvention.

The invention thus provides an unexpectedly convenient and ortuitoussolution to the problem of clear spot formation in the phosphor coatingat gas lill and without requiring any extensive modifications in lampmaking machinery or processing techniques. Furthermore, the problem issolved without running aioul of the danger of `emission coatingdislodgement from the cathode which is encountered with an axialblow-out mount design.

The preferred embodiment of the invention which has been described indetail and illustrated in the drawing is intended as exemplary and notin order to limit the invention thereto. The scope of the invention isto be determined by the appended claims.

Wha-t we claim as new and desire to secure by Letters Patent of theUnited States is:

1. A fluorescent lamp mount comprising a flared stein "abe and anexhaust tube extending axially thercinto and torminU a juncturetherewith constituting a vitreous press, lead-in wires projectingthrough said pr ss, and a bl rout aperture formed in one side of saidpress and cornmunicating with said exhaust tube, said blow-out aperturebeing ilared outwardly and vwidened relative to the exhaust tube passageso that a gas jet issuing therefrom issues with reduced velocity and ina quasitaxial direction.

2. A fluorescent lamp mount comprising a flared stern tube `and anexhaust tube extending axially thereinto and forming a juncturetherewith constituting a vitreous press, 'lead-in wires projectingthrough said press, and a blow- `out aperture formed in one side of saidpress and communicating with said exhaust tube, said blow-out aperturebeing continued into a groove formed in said one side of the press 'andextending towards the end thereof.

3. A iuorescent lamp mount comprising a ilared sten tube and an exhausttube extending axially thereinto and forming a juncture therewithconstituting a vitreous press, lead-in wires projecting through saidpress and supporting an electrode, and a blow-out aperture formed in oneside of said press and communicating with said exhaust tube, saidblow-out aperture being iiared outwardly and widened relative to theexhaust tube passage and being continued into a grooved channel formedin said one side of the press and extending towards the end t creci.

4. A fluorescent lamp mount comprising a ilared stem tube and an exhausttube extending axially thereinto and forming a juncture therewithconstituting a vitreous j press, lead-in wires proje ting through saidpress and supporting a filament transversely to the axis of said exhausttube, and a blow-out aperture `termed in one side of said press andcommunicating with said exhaust tube, said blow-out aperture beingflared outwardly and widened relative to the exhaust tube passage andbeing extended as a channel in said one side of the press between saidlead wires substantially to tre end of said press so that a gas jetissuing from said aperture issues with reduced velocity in a directionmaking a shallow angle with said axis but avoiding said filament.

5. A fluorescent lamp mount `comprising a iiared stem tube and anexhaust tube extending axially thereinto and forming a juncturetherewith constituting a vitreous press, lead-tin wires projectingthrough said press and Supporting a filament across the projected axisof said exhaust tube, and a blow-out aperture formed in one side of saidpress and communicating with said exhaust tube, said blo: -out aperturelbeing widened relative to the exhaust tube passage and `being continuedinto a grooved channel formed in said one side of the press andextending towards 4the end thereof, the central portion of the channelwall being inclined to said one side at an angle between 5 and 15 to theaxis of said exhaust tube.

6. A iiuorescent lamp mount as` defined in claim 5 wherein said centralportion or" the channel wall is inclined to said one side at an angle ofapproximately 9 to the axis of said exhaust tube.

7. A fluorescent lamp comprising an elongated tubular envelopeinternally coated with phosphor and having mounts sealed into the endsthereof, at least one of said mounts comprising a flared stern tuberandan kexhaust tubeA penetrating thereinto and forming a juncture therewithconstituting a vitreouspress, lead-in wires projecting through said:press and supporting a filament Wit-hin said lamp, and a blow-outaperture formed Vin one side of said y press and communicating withsaid-exhaust tube, said yblowout aperture being kflared outwardly andwidened relative to the exhaust ltube passage so that a gas jet issu-`ing therefrom into said lamp at gas lill issues with reduced velocityand in a quai-axialfdirection relative to said enveloper in order toavoid blowing phosphor oil saidV envelope Wall.

, 8. A iluorescent lampcornprising an elongated tubular envelopeinternally coated with phosphor 4and having mounts sealed into the endstherof, at least one of said mounts comprising a flared stern Itube andan exhaust tube penetrating thereinto and forming a juncture therewithconstituting a vitreous press, lead-in Wires projecting through saidpress and supporting a filament with-in said lamp, and a blow-outaperture formed in one side of said press and communicating with saidexhaust tube, said blow-out aperture being lared outwardly and widenedrelative ato the exhaust tube passage and continued into a groovedchannel )formed in said one side of the press and exten-ding to the endthereof, whereby a gas jet 9. y A jlluorescent lamp comprising anelongated tubular envelope internally coated with phosphor and nhavingmounts sealed into the ends thereof, at least one of said mountscomprising a flared stem tube and an exhausttube penetrating rthereintoand forming a juncture therewith constituting a vitreous press, lead-inwires projecting through said press and, supporting a filament withinsaid lamp across its axis, and a blow-out aperture formed in one side ofsaid press and communicating with said exreleased into the lamp throughsaid exhaustY tubeis delected olf axis sufciently lto avoid strikingsaid filament. l0. A lamp :as .in claim 9 wherein said grooved channelis inclined at an angle or approximately 9 to said lampV axis.

issuing from said aperture into said lamp at gas ll issues Y withreduced yvelocity and in `a quasi-axialV direction rela-y tive to saidenvelope in order to avoid blowing-phosphor olf said envelope wall. L Y

- References Cited in the tile of this patent UNITED STATES PATENTS Y2,692,347

2,991,386 Szigeti et al. V `l'uly 4, i961 Mason oor. i9, 1954

7. A FLUORESCENT LAMP COMPRISING AN ELONGATED TUBULAR ENVELOPEINTERNALLY COATED WITH PHOSPHOR AND HAVING MOUNTS SEALED INTO THE ENDSTHEREOF, AT LEAST ONE OF SAID MOUNTS COMPRISING A FLARED STEM TUBE ANDAN EXHAUST TUBE PENETRATING THEREINTO AND FORMING A JUNCTURE THEREWITHCONSTITUTING A VITREOUS PRESS, LEAD-IN WIRES PROJECTING THROUGH SAIDPRESS AND SUPPORTING A FILAMENT WITHIN AID LAMP, AND A BLOW-OUT APERTUREFORMED IN ONE SIDE OF SAID PRESS AND COMMUNICATING WITH SAID EXHAUSTTUBE, SAID BLOWOUT APERTURE BEING FLARED OUTWARDLY AND WIDENED RELATIVETO THE EXHAUST TUBE PASSAGE SO THAT A GAS JET ISSUING THEREFROM INTOSAID LAMP AT GAS FILL ISSUES WITH REDUCED VELOCITY AND IN A QUAI-AXIALDIRECTION RELATIVE TO SAID ENVELOPE IN ORDER TO AVOID BLOWING PHOSPHOROFF SAID ENVELOPE WALL.